Signal generator



Dec. 24, 1946. R. c. HERGENROTHER SIGNAL GENERATOR Filed Feb. 9, 1944 2 Sheets-Sheet 2 Pulses Applied to Tube 10 v Output Current of Tube l0 Pulses Applied to Tube l0 Output Current of Tube l0 1 Differential Combination of Currents Voltage at terminals l7, l8

Voltage, Tube IO Voltage, Tube l0 INVENTOR RUDOLF C. HERGENROTHER Patented Dec. 24, 1946 SIGNAL GENERATOR Rudolf C. Hergenrother, Beechhurst, N. Y., as-

signor, by mesne assignments, to Hazeltine Research, Inc, Chicago, 111., a corporation of Illinois Application February 9, 1944, Serial No. 521,637

10 Claims. 1

The present invention relates to signal generators adapted to provide pulses of electrical energy and relates particularly to pulse generators of a type adapted to supply pulses having a relatively large energy content.

In pulse-wave generators of a type commonly employed in signal-translating. and control circuits it is customary to use high-vacuum electron tubes. Since high-vacuum electron tubes are high-impedance devices, the peak power output of generators utilizing this type of tube is generally limited by the peak Voltage which may be applied to the tube. In order to avoid the disadvantages and limitations attendant upon the use of tubes of this type in a pulse generator, it has been proposed in accordance with one prior art arrangement to employ a low-im pedance vapor-electric discharge device through which a condenser discharges into a load circuit. However, since such an arrangement has a discharge characteristic or decay curve of exponential form, it is necessary, when rectangular pulses are desired, to shape the output pulses into the desired form by additional circuit arrangements. Such arrangements generally depend upon more or less complicated Wave-shaping networks. It has been found that such networks, while producing approximately rectangular pulses, are limited in the steepness of the sides of the pulse. It is therefore desirable to provide a pulse-wave generator which utilizes the superior power performance of the vaporelectric discharge device and which at the same time avoids the limitations of the prior art arrangements mentioned above.

It is an object of the present invention, therefore, to provide a new and improved pulse-signal generator which is free from one or more of the limitations and disadvantages of the prior art arrangements mentioned above. 7

It is an additional object of the invention to provide a pulse-wave generator which does not require the use of wave-shaping networks, such as limiting or clipping circuits, or ultimate dependence upon high-vacuum tubes.

It is another object of the invention to provide a simple, economical means for generating pulses of relatively high power.

It is a further object of the invention to pro vide an improved pulse-signal generator for generating pulses defined by relatively steep sides.

In accordance with the invention, a signal generator comprises means for developing a first signal of pulse wave form each pulse of which has a steep edge portion and an exponential portion. The generator also includes means for de veloping a second signal of pulse Wave form each pulse of which has a smaller amplitude than each pulse of the first signal and ha a corresponding steep edge portion and an exponential edge portion similar to, and coextensive in time with, at least a part of the first-mentioned exponential edge portion. The signal generator additionally includes means for diiferentially combining these signals to obtain a resultant signal of substantially rectangular-pulse wave form'having substantially zero amplitude during this coextensive time.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the accompanying drawings, Fig. 1 is a circuit diagram, partly schematic, of one embodiment of the present invention; Fig. 2 comprises a set of curves used in explaining the operation of the Fig. 1 embodiment; Fig. 3 is a circuit diagram, partly schematic, of a modified form of the invention; and Fig. 4 illustrates a further modified form of the invention.

Coming now to a detailed description of the invention, the embodiment illustrated in Fig. 1 comprises a signal generator including means for developing a first signal of pulse wave form each pulse of which has a steep edge portion and an exponential edge portion. This means comprises a vapor-electric discharge device or gaseous tube H] and a condenser ll, included in the output circuit of the tube and adapted to be discharged through the tube. Also serially included with condenser I! in the output circuit of tube It are an inductor l2 and a cathode resistor I3. Tube ii! is provided with a source of anode potential +B connected through a resistor I l to its anode.

The value of resistor I4 is so chosen that, following the discharge of condenser H, the tube current is reduced below the threshold value for which the tube remains conducting.

The Fig. 1 embodiment also comprises means for developing a second signal of pulse wave form each pulse of which has a smaller amplitude than each pulse of the first signal and has a corresponding steep edge portion and an exponential edge portion similar to, and coextensive in time with, at least a part of the exponential edge portion of the signal developed by the first-described means. This means is generally similar to the first -means described above and comprises a condenser i 3 starts to discharge vapor-electric discharge device or gaseous tube l and a condenser H included in the output circuit of tube it and adapted to be discharged through the tube. Elements of this means which are identical to elements of the first-mentioned means are represented. by the same reference numerals primed. it should be noted, howev,er, that the voltageof source +13 is greater than that of source +B'.

The Fig. 1 embodiment also comprises means for diiferentially combining the signals developed by the two first-described means to produce a resultant signal having substantially zero amplitude during the above-mentioned coextensive time. This means comprises a transformer l which has a secondary winding 16, coupled to output terminals Hand it, and includes as primary windings the inductors l2 and I2. The primary inductors are wound in the same sense and are grounded at their common terminal, the junction of resistors i3 and It also being grounded. to complete the discharge paths of the tubes.

The Fig. 1 embodiment is provided with means for supplying first and second pulse signals of relatively small energy content having a predetermined interval therebetween for controlling the operation of the tubes iii and IE! to provide the desired output signal. Specifically, the input circuits of tubes ill and lil are coupled with opposite polarity through inductors 2i and 2| of a transformer 26 to a common control-signal source !9. The control elements of the tubes are providedwith an appropriate source of bias potential 22 which is connected through a gridcurrent limiting resistor 23 to the junction of inductors 2| and 21'. The source it of control signals comprises a generator of conventional design adapted to generate adjacent pulses of opposite polarity, which are spaced apart by a time interval equal to the desired output pulse duration.

Reference is made to the curves of Fig. 2 for a description of the operation of the Fig. 1 embodiment of the invention. It is assumed that a first control or triggering pulse from source l9, as represented by curve A, is applied to the transformer 2%! and it will be seen that this pulse, being of positive polarity as applied to the control electrode of tube it], causes tube l6 to become conductive. Thereafter the gas in tube .Hl ionizes, the control electrode loses control, and through the tube at a high rate, as represented by curve B. Since this first triggering pulse is of negative polarity as applied to the control electrode of tube iii, no anode-current flow occurs therein due to this pulse.

During the interval between the first and second control pulses of curve A, condenser H continues to discharge exponentially. The second pulse of curve A, being of negative polarity as applied to the control electrode of tube Ill, does not affect the discharge current thereof. However, this pulse, being of positive polarity as applied to the control electrod of tube ill, as represented by curve C, renders tube Iii conductive. Condenser I! therefore discharges through tube H! at a high rate, as represented by curve D. The flow of current through inductor I2 is effective to induce a voltage in inductor it and to decrease the impedance of inductor l2 due to the mutual coupling between these inductors. Therefore, the current throughinductor l2 and therate of discharg of condenser I I increase at instant t1, as indicated by curve B. The circuits are so proportioned that tubes is and Iii develop signals having similar exponential portions following the time t1, as rep- 5 resented by the curves B and D, respectively. The combined signal output of tubes l0 and I0 is illustrated by curve E and the shaded areas of the curve have equal and opposite eflfects on the voltage induced in secondary winding It so "that the voltage at terminals l7 and i8 is substantially as represented by curve F. The voltage across tubes lil and I0, respectively, is represented in curves G and H. At time 122 condensers II and H have been discharged below the extinction potential and the tubes return to their initial high impedance after de-ionization has been completed. Following the time t2 the condensers H and H are slowly charged from theirrespective source +3 and +B and, after they have been charged, the above-described cycle can be repeated.

The result of this cycle of operations is the generation of a signal of high energy content at output terminals E1, Hi, this signal having sharp leading and trailing edges and substantially zero amplitud during the coextensive time of the discharge of condensers Ii and H, and having a duration determined by the interval between the first and second of control pulses generated by source IS.

The embodiment illustrated in Fig. 3 is essentially similar to that shown in Fig. 1 and like circuit elements have identical reference numerals. The Fig. 3 embodiment also is suitable for the generation of signals of high energy content at a repetition rate determined by the repetition rate of the applied control signals. The Fig. 3 embodiment differs "from that of Fig. 1 in that it comprises a pulse generator 19 of conventional design, adapted to generate rectangular pulses of small energy content, and means for difierentiatin these pulses to derive therefrom adjacent control pulses of opposite polarity. This means comprises a differentiating circuit including a condenser 24 and resistors 25 and .25 individually included in the input circuits of tubes ill and I0, respectively, and having a common point connected to resistor 23. Pulse generator l9 has an output circuit connected to this difierentiating circuit. Shielding electrodes are prefe'rably provided in tubes H1 and I0 and are negatively biascdby source 22 through resistors 28 and 28, respectively.

The operation of the Fig; 3 embodiment is generally similar to that of the Fig. l embodiment. However, in this case, a rectangular control pulse developed by generator I9 is difierentiated by the circuit comprising condenser 24 and resistors 25 and 25 so that resultant trig- 0 gering pulses, as represented by curves A and C,

are derived at the initiation and termination of the control pulse and applied in opposite polarity to tubes 19 and i0, respectively. The remainder of the cycle of events occurring in the circuits following the application of the triggering pulses to tubes l0 and I0 is the same as that occurring in the Fig. 1 embodiment. In

this embodiment, the duration of the output signal is determined by the interval between the leading and trailing edges of the control pulse.

.The embodiment illustrated in Fig. 4 is essentially similar to that shown in Fig. 3 and like circuit elements have identical reference numerals. The embodiment of Fig. i differs from that .of Fig.3 in that the meansfor producing the desired first and second triggering pulses comprises a pulse generator and a delay network instead of a pulse generator and difierentiating circuit. Thus, this means comprises pulse generator t9 which has an output circuit connected across resistor 25 to the input circuit of tube l and a delay network 32 of conventional design. This network 32 has an input circuit connected to the output circuit of control-signal generator l9 and an output circuit connected across resistor 25' in the input circuit of tube l 0'.

The operation of the Fig. 4 embodiment is generally similar to that of the Fig. 3 embodiment. However, the control pulse from generator I9 is applied directly to the input circuit of tube l0 and constitutes the triggering pulse for tube l0 and there is derived from the control pulse a delayed pulse which appears in the output circuit of network 32 and which is utilized as the triggering pulse applied to tube l 0'. These triggering pulses may be of any desired shape, such as rectangular or triangular, and correspond in function to the first pulse illustrated in curve A and the second pulse illustrated in curve 0. Following the application of these pulses to tubes I 0 and I0, respectively, the operation of the embodiment of Fig. 4 is the same as that of the Fig. 3 embodiment. However, it will be noted that the width of the resultant pulse in the Fig. 4 arrangement is dependent upon the time delay of network 32 and is independent of the width of the control pulse supplied by unit I9.

While it is not proposed to limit the invention to any specific circuit parameters, the following parameters have been found suitable in an arrangement in accordance with the Fig. 3

embodiment of the invention, when operating at a repetition rate of sixty pulses per second:

Transformer l5 Primary 42 turns of No.

i 20 enameled wire, center tapped; secondary 240 turns of No. 30 enameled wire; core, Hipersil 046, shell type; coil, size A," x square, /16" long.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall Within the true spirit and scope of the invention.

What is claimed is:

1. A signal generator comprising, means for developing a first signal of pulse wave form each pulse of which has a steep edge portion and an exponential edge portion, means for developing a second signal of pulse wave form each pulse of which has a smaller amplitude than said each pulse of said first signal and has a corresponding steep edge portion and an exponential edge portion similar to, and coextensive in time with, at least a part of said firstmentioned exponential edge portion, and means for differentially combining said signals to obtain a resultant signal of substantially rectangularpulse wave form having substantially zero amplitude during said coextensive time.

2. A signal generator comprising, means including a control-electrode-controlled vaporelectric discharge device for developing a first signal of pulse wave form each pulse of which has a steep edge portion and an exponential edge portion, means including a control-electrode-controlled vapor-electric discharge device for developin a second signal of pulse wave form each pulse of Which has a smaller amplitude than said each pulse of said first signal and has a corresponding steep edge portion and an exponential edge portion similar to, and coextensive in time with, at least a part of said first-mentioned exponential edge portion, and means for differentially combining said signals to obtain a resultant signal of substantially rectangular-pulse wave form having substantially zero amplitude during said coextensive time.

3. A signal generator comprising, means for developing a first signal of pulse wave form each pulse of which has a steep edge portion and an exponential edge portion, means for developing a second signal of pulse wave form each pulse or" which has a smaller amplitude than said each pulse of said first signal and has a corresponding steep edge portion and an exponential edge portion similar to, and coextensive in time with, at least a part of said first-mentioned exponential edge portion, and means comprising a transformer having a primary Winding in the output circuit of each of said first-mentioned means for differentially combining said signals to obtain a resultant signal of substantially rectangularpulse Wave form having substantially zero amplitude during said coextensive time.

4. Asignal generator for developing a pulse of relatively large energy content comprising, means for supplying a control pulse of relatively small energy content, means for differentiating said pulse to obtain triggering pulses of opposite 0 polarity at the initiation and termination of said pulse, means including a vapor-electric discharge device and responsive to the first of said triggering pulses for developing a first signal of pulse wave form each pulse of which has a steep edge portion and an exponential edge portion, means including a vapor-electric discharge device and responsive to the second of said triggering pulses for developing a second signal of pulse Wave form each pulse of which has a smaller amplitude than said each pulse of said first signal and has a corresponding steep edge portion and an exponential edge portion similar to, and coextensive in time with, at least a part of said first-mentioned exponential edge portion, and means for differentially combining said signals to obtain a resultant signal of substantially rectangular-puls'e wave-form having substantially zero amplitude during said coextensive time.

5. A signal generator for developing a pulse of relatively large energy content comprising, means for supplying first and second pulses of relatively small energy content, said pulses having a predetermined interval therebetween, means ineluding a vapor-electric discharge device and responsive to the first of said pulses for developing a first signal of pulse wave form each pulse of which has a steep edge portion and an exponential edge portion, means including a vaporelectric discharge device and responsive to the second of said pulses for developing a second signal of pulse wave form each pulse of which has a smaller amplitude than said each pulse of said first signal and has a corresponding steep edge portion and an exponential edge portion similar to, and coextensive in time with, at least a part of said first-mentioned exponential edge portion, and means for differentially combining said signal to obtain a resultant signal of substantially rectangular-pulse wave form having substantially zero amplitude during said coextensive time and a duration determined by the interval between said first-named pulses.

6. A signal generator for developing a pulse of relatively .large energy content comprising, means for developing a first control pulse of relatively small energy content, means independent of the duration of said first control pulse for deriving therefrom a second control pulse delayed by predetermined time interval, means including a vapor-electric discharge device and responsive to said first control pulse for developing a first signal of pulse wave form each pulse of which has a steep edge portion and an exponential edge portion, means including a vapor-electric discharge device and responsive to the second of said control pulses for developing a second signal of pulse wave form each pulse of which has a smaller amplitude than said each pulse of said first signal and has a corresponding steep edge portion and an exponential edge portion similar to, and coextensive in time with, at least a part of said first-mentioned exponential edge portion, and means for diiierentially combining said signals to obtain a resultant signal of substantially rectangular-pulse wave form having substantially zero amplitude during said coextensive time and a duration independent of the duration of said first control pulse.

'7. A signal generator for developing a pulse of relatively large energy content comprising, means for developing a pulse of relatively small energy content, said pulse having two sharply defined discontinuities, means responsive to the first of said discontinuities for developing a first signal of pulse wave form each pulse of which has a steep edge portion and an exponential edge portion, means responsive to the second of said discontinuities for developing a second signal of pulse wave form each pulse of which has a smaller amplitude than said each pulse or said first signal and has a corresponding steep edge portion and an exponential edge portion similar to, and coextensive in time with, at least a part of said first-mentioned exponential edge portion, and means for differentially combining said signals to obtain a resultant signal of substantially rectangular-pulse wave-form having substantially zero amplitude during said coextensive time.

8. A signal generator for developing a pulse of relatively large energy content comprising, means for developing a first control pulse of relatively small energy content, means for deriving from said first control pulse a second control pulse delayed by a predetermined time interval, means including a vapor-electric discharge device and responsive to said first control pulse for developing a first signal of pulse wave form each pulse of which has a steep edge portion and an exponential edge portion, means including a vapor-electric discharge device and responsive to said second control pulse for developing a second signal of pulse wave form each pulse of which has a smaller amplitude than said each pulse of said first signal and has a corresponding steep edge portion and an exponential edge portion similar to, and coextensive in time with, at least a part of said first-mentioned exponential edge portion, and means for differentially combining said signals to obtain a resultant signal of substantially rectangular-pulse wave form having substantially zero amplitude during said coextensive time and a duration determined by said predetermined time interval.

9. A signal generator for developing repeating pulses of relatively large energy content comprising, means for developing first and second triggering pulses of relatively small energy content at a predetermined repetition rate, means responsive to said first triggering pulse and including a vapor-electric discharge device having a condenser included in its output circuit for developing from each said first triggering pulse a first signal of pulse wave form each pulse of which has a steep edge portion and an exponential edge portion, means responsive to said second triggering pulse and including a vapor-electric discharge device having a condenser included in its output circuit for developing from each said second triggerin pulse a second signal of pulse wave form each pulse of which has a smaller amplitude than said each pulse of said first signal and has a corresponding steep edge portion and a similar exponential edge portion coextensive in time with at least a part of a corresponding one of said first-mentioned exponential edge portions, means including a timeconstant circuit for charging said first-mentioned condenser to a desired potential at said repetition rate, and means including a time-constant circuit for charging said second-mentioned con denser to a different potential at said repetition rate, said time-constant circuits being so proportioned that the magnitudes of said timecoextensive exponential edge portions are equal, and means for differentially combinin said first and second signals to obtain resultant signals of substantially rectangular-pulse wave form having substantially zero amplitude during said coextensive times.

10. A signal generator comprising, means for developing a first signal of pulse wave form each pulse of which has an exponential edge portion at least a part of which is undesirable, means for developing a second signal of pulse wave form each pulse of which has a steep edge portion and an exponential edge portion of substantially the same amplitude and wave form as said part of said undesirable exponential edge portion of said first signal, and means for difierentially combining said signals to obtain a resultant signal of pulse wave form each pulse of which has in point of time a steep edge portion corresponding to the steep edge portion of said each pulse of said second signal and substantially zero amplitude during the interval corresponding to the undesirable part of the exponentialedge portion of said each pulse of said first signal.

RUDOLF C. HERGENROTHER. 

